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KRAS is vulnerable to reversible switch-II pocket engagement in cells
James D Vasta1, D Matthew Peacock2, Qinheng Zheng2
1Promega Corporation, Madison, WI, USA.
Abstract:
Current small-molecule inhibitors of KRAS(G12C) bind irreversibly in the switch-II pocket (SII-P), exploiting the strong nucleophilicity of the acquired cysteine as well as the preponderance of the GDP-bound form of this mutant. Nevertheless, many oncogenic KRAS mutants lack these two features, and it remains unknown whether targeting the SII-P is a practical therapeutic approach for KRAS mutants beyond G12C. Here we use NMR spectroscopy and a cellular KRAS engagement assay to address this question by examining a collection of SII-P ligands from the literature and from our own laboratory. We show that the SII-Ps of many KRAS hotspot (G12, G13, Q61) mutants are accessible using noncovalent ligands, and that this accessibility is not necessarily coupled to the GDP state of KRAS. The results we describe here emphasize the SII-P as a privileged drug-binding site on KRAS and unveil new therapeutic opportunities in RAS-driven cancer.
Insights
The switch-II pocket (SII-P) of KRAS mutants, beyond G12C, is accessible to noncovalent inhibitors. This finding expands therapeutic strategies for RAS-driven cancers by highlighting the SII-P as a druggable target.
Area of Science:
- Oncology
- Molecular Biology
- Medicinal Chemistry
Background:
- Current KRAS(G12C) inhibitors target the switch-II pocket (SII-P) irreversibly.
- Many oncogenic KRAS mutants lack the features exploited by these inhibitors, leaving their SII-P druggability uncertain.
Purpose of the Study:
- To investigate the accessibility of the SII-P in KRAS mutants beyond G12C.
- To explore the potential of noncovalent ligands for targeting these mutants.
Main Methods:
- Utilized NMR spectroscopy to analyze KRAS mutants.
- Employed a cellular KRAS engagement assay to assess ligand binding.
- Examined a library of switch-II pocket ligands.
Main Results:
- The SII-P of various KRAS hotspot mutants (G12, G13, Q61) is accessible to noncovalent ligands.
- Accessibility of the SII-P is not strictly dependent on the GDP-bound state of KRAS.
- Demonstrated broader applicability of SII-P targeting.
Conclusions:
- The SII-P is a privileged drug-binding site across multiple KRAS mutants.
- Noncovalent inhibitors offer a viable therapeutic strategy for a wider range of KRAS-driven cancers.
- Unveiled new avenues for developing targeted cancer therapies.
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